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Subject[PATCH v6 3/6] regmap: Add regmap_noinc_read API
Date
From: Crestez Dan Leonard <leonard.crestez@intel.com>

The regmap API usually assumes that bulk read operations will read a
range of registers but some I2C/SPI devices have certain registers for
which a such a read operation will return data from an internal FIFO
instead. Add an explicit API to support bulk read without range semantics.

Some linux drivers use regmap_bulk_read or regmap_raw_read for such
registers, for example mpu6050 or bmi150 from IIO. This only happens to
work because when caching is disabled a single regmap read op will map
to a single bus read op (as desired). This breaks if caching is enabled and
reg+1 happens to be a cacheable register.

Without regmap support refactoring a driver to enable regmap caching
requires separate I2C and SPI paths. This is exactly what regmap is
supposed to help avoid.

Suggested-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Crestez Dan Leonard <leonard.crestez@intel.com>
Signed-off-by: Stefan Popa <stefan.popa@analog.com>
Reviewed-by: Jonathan Cameron <jic23@kernel.org>
---
drivers/base/regmap/internal.h | 3 ++
drivers/base/regmap/regmap.c | 79 +++++++++++++++++++++++++++++++++++++++++-
include/linux/regmap.h | 19 ++++++++++
3 files changed, 100 insertions(+), 1 deletion(-)

diff --git a/drivers/base/regmap/internal.h b/drivers/base/regmap/internal.h
index 53785e0..a6bf34d63 100644
--- a/drivers/base/regmap/internal.h
+++ b/drivers/base/regmap/internal.h
@@ -94,10 +94,12 @@ struct regmap {
bool (*readable_reg)(struct device *dev, unsigned int reg);
bool (*volatile_reg)(struct device *dev, unsigned int reg);
bool (*precious_reg)(struct device *dev, unsigned int reg);
+ bool (*readable_noinc_reg)(struct device *dev, unsigned int reg);
const struct regmap_access_table *wr_table;
const struct regmap_access_table *rd_table;
const struct regmap_access_table *volatile_table;
const struct regmap_access_table *precious_table;
+ const struct regmap_access_table *rd_noinc_table;

int (*reg_read)(void *context, unsigned int reg, unsigned int *val);
int (*reg_write)(void *context, unsigned int reg, unsigned int val);
@@ -181,6 +183,7 @@ bool regmap_writeable(struct regmap *map, unsigned int reg);
bool regmap_readable(struct regmap *map, unsigned int reg);
bool regmap_volatile(struct regmap *map, unsigned int reg);
bool regmap_precious(struct regmap *map, unsigned int reg);
+bool regmap_readable_noinc(struct regmap *map, unsigned int reg);

int _regmap_write(struct regmap *map, unsigned int reg,
unsigned int val);
diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index 3bc8488..0360a90 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -168,6 +168,17 @@ bool regmap_precious(struct regmap *map, unsigned int reg)
return false;
}

+bool regmap_readable_noinc(struct regmap *map, unsigned int reg)
+{
+ if (map->readable_noinc_reg)
+ return map->readable_noinc_reg(map->dev, reg);
+
+ if (map->rd_noinc_table)
+ return regmap_check_range_table(map, reg, map->rd_noinc_table);
+
+ return true;
+}
+
static bool regmap_volatile_range(struct regmap *map, unsigned int reg,
size_t num)
{
@@ -766,10 +777,12 @@ struct regmap *__regmap_init(struct device *dev,
map->rd_table = config->rd_table;
map->volatile_table = config->volatile_table;
map->precious_table = config->precious_table;
+ map->rd_noinc_table = config->rd_noinc_table;
map->writeable_reg = config->writeable_reg;
map->readable_reg = config->readable_reg;
map->volatile_reg = config->volatile_reg;
map->precious_reg = config->precious_reg;
+ map->readable_noinc_reg = config->readable_noinc_reg;
map->cache_type = config->cache_type;

spin_lock_init(&map->async_lock);
@@ -1285,6 +1298,7 @@ int regmap_reinit_cache(struct regmap *map, const struct regmap_config *config)
map->readable_reg = config->readable_reg;
map->volatile_reg = config->volatile_reg;
map->precious_reg = config->precious_reg;
+ map->readable_noinc_reg = config->readable_noinc_reg;
map->cache_type = config->cache_type;

regmap_debugfs_init(map, config->name);
@@ -2564,7 +2578,70 @@ int regmap_raw_read(struct regmap *map, unsigned int reg, void *val,
EXPORT_SYMBOL_GPL(regmap_raw_read);

/**
- * regmap_field_read() - Read a value to a single register field
+ * regmap_noinc_read(): Read data from a register without incrementing the
+ * register number
+ *
+ * @map: Register map to read from
+ * @reg: Register to read from
+ * @val: Pointer to data buffer
+ * @val_len: Length of output buffer in bytes.
+ *
+ * The regmap API usually assumes that bulk bus read operations will read a
+ * range of registers. Some devices have certain registers for which a read
+ * operation read will read from an internal FIFO.
+ *
+ * The target register must be volatile but registers after it can be
+ * completely unrelated cacheable registers.
+ *
+ * This will attempt multiple reads as required to read val_len bytes.
+ *
+ * A value of zero will be returned on success, a negative errno will be
+ * returned in error cases.
+ */
+int regmap_noinc_read(struct regmap *map, unsigned int reg,
+ void *val, size_t val_len)
+{
+ size_t read_len;
+ int ret;
+
+ if (!map->bus)
+ return -EINVAL;
+ if (!map->bus->read)
+ return -ENOTSUPP;
+ if (val_len % map->format.val_bytes)
+ return -EINVAL;
+ if (!IS_ALIGNED(reg, map->reg_stride))
+ return -EINVAL;
+ if (val_len == 0)
+ return -EINVAL;
+
+ map->lock(map->lock_arg);
+
+ if (!regmap_volatile(map, reg) || !regmap_readable_noinc(map, reg)) {
+ ret = -EINVAL;
+ goto out_unlock;
+ }
+
+ while (val_len) {
+ if (map->max_raw_read && map->max_raw_read < val_len)
+ read_len = map->max_raw_read;
+ else
+ read_len = val_len;
+ ret = _regmap_raw_read(map, reg, val, read_len);
+ if (ret)
+ goto out_unlock;
+ val = ((u8 *)val) + read_len;
+ val_len -= read_len;
+ }
+
+out_unlock:
+ map->unlock(map->lock_arg);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(regmap_noinc_read);
+
+/**
+ * regmap_field_read(): Read a value to a single register field
*
* @field: Register field to read from
* @val: Pointer to store read value
diff --git a/include/linux/regmap.h b/include/linux/regmap.h
index 4f38068..19df946 100644
--- a/include/linux/regmap.h
+++ b/include/linux/regmap.h
@@ -268,6 +268,13 @@ typedef void (*regmap_unlock)(void *);
* field is NULL but precious_table (see below) is not, the
* check is performed on such table (a register is precious if
* it belongs to one of the ranges specified by precious_table).
+ * @readable_noinc_reg: Optional callback returning true if the register
+ * supports multiple read operations without incrementing
+ * the register number. If this field is NULL but
+ * rd_noinc_table (see below) is not, the check is
+ * performed on such table (a register is no increment
+ * readable if it belongs to one of the ranges specified
+ * by rd_noinc_table).
* @disable_locking: This regmap is either protected by external means or
* is guaranteed not be be accessed from multiple threads.
* Don't use any locking mechanisms.
@@ -295,6 +302,7 @@ typedef void (*regmap_unlock)(void *);
* @rd_table: As above, for read access.
* @volatile_table: As above, for volatile registers.
* @precious_table: As above, for precious registers.
+ * @rd_noinc_table: As above, for no increment readable registers.
* @reg_defaults: Power on reset values for registers (for use with
* register cache support).
* @num_reg_defaults: Number of elements in reg_defaults.
@@ -344,6 +352,7 @@ struct regmap_config {
bool (*readable_reg)(struct device *dev, unsigned int reg);
bool (*volatile_reg)(struct device *dev, unsigned int reg);
bool (*precious_reg)(struct device *dev, unsigned int reg);
+ bool (*readable_noinc_reg)(struct device *dev, unsigned int reg);

bool disable_locking;
regmap_lock lock;
@@ -360,6 +369,7 @@ struct regmap_config {
const struct regmap_access_table *rd_table;
const struct regmap_access_table *volatile_table;
const struct regmap_access_table *precious_table;
+ const struct regmap_access_table *rd_noinc_table;
const struct reg_default *reg_defaults;
unsigned int num_reg_defaults;
enum regcache_type cache_type;
@@ -946,6 +956,8 @@ int regmap_raw_write_async(struct regmap *map, unsigned int reg,
int regmap_read(struct regmap *map, unsigned int reg, unsigned int *val);
int regmap_raw_read(struct regmap *map, unsigned int reg,
void *val, size_t val_len);
+int regmap_noinc_read(struct regmap *map, unsigned int reg,
+ void *val, size_t val_len);
int regmap_bulk_read(struct regmap *map, unsigned int reg, void *val,
size_t val_count);
int regmap_update_bits_base(struct regmap *map, unsigned int reg,
@@ -1196,6 +1208,13 @@ static inline int regmap_raw_read(struct regmap *map, unsigned int reg,
return -EINVAL;
}

+static inline int regmap_noinc_read(struct regmap *map, unsigned int reg,
+ void *val, size_t val_len)
+{
+ WARN_ONCE(1, "regmap API is disabled");
+ return -EINVAL;
+}
+
static inline int regmap_bulk_read(struct regmap *map, unsigned int reg,
void *val, size_t val_count)
{
--
2.7.4
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